Apparatus for forming center-unwindable rolls of perforated plastic film

Abstract

An apparatus is disclosed for winding strips or tubes of plastic film into center-unwindable rolls having a diameter of at least about 3 inches and for unloading the wound rolls without telescoping thereof. Bare expandable winding shafts are provided which comprise a fixed vacuum leaf and a plurality of movable leaves controlled by an elongated air bladder, the contracted diameter being at least about one-quarter inch less than the expanded diameter. Each leaf also has an outer surface having a selected slipperiness toward the film surface.

What is claimed is: 
     
       1. A bare expandable winding shaft for winding transversely perforated plastic film to form a plurality of center-unwindable rolls at a plurality of winding positions, said shaft comprising: A. a plurality of elongated leaves forming a generally cylindrical outer surface upon which said rolls are wound;   B. an intermediate tubular shaft body having apertures for radially movable buttons;   C. an elongated central air bladder which is arranged axially within said shaft body, said bladder being adapted to move said buttons radially for changing the effective diameter of said outer surface through an expansion range of at least about 0.25 inch between an expanded diameter and a relaxed diameter, said expanded diameter being at least about 3 inches;   D. a vacuum leaf which replaces one of said movable leaves at said expanded diameter and is immovably supported in fixed radial position on said tubular shaft body;   E. a plurality of roll winding locations that are spaced axially apart along said shaft, each said roll location having an axially grouped plurality of holes in said vacuum leaf for contacting said plastic film when said rolls are being wound on said shaft at said expanded diameter;   F. a vacuum means which is: (1) aligned with the axis of said expandable shaft,   (2) capable of being rapidly connected to a high-capacity vacuum source, and   (3) in fluid communication with said holes in said outer surface of said vacuum leaf; and     G. a friction-reducing means on said outer surface for imparting a selected maximum coefficient of friction between said outer surface and said plastic film.   
     
     
       2. The winding shaft of claim 1, wherein said vacuum source contains a vacuum of at least about 20 inches Hg. 
     
     
       3. The winding shaft of claim 1, wherein said coefficient of friction is up to about 1.10. 
     
     
       4. The winding shaft of claim 3, wherein said coefficient of friction is up to about 0.60. 
     
     
       5. The winding shaft of claim 4, wherein said friction-reducing means is a Teflon coating on said outer surface and a silicone spray coating over said Teflon coating. 
     
     
       6. The winding shaft of claim 5, wherein said Teflon coating is a Teflon impregnated Sanford hard lube finish that is about 0.0002 inch thick. 
     
     
       7. The winding shaft of claim 3, wherein said friction-reducing means is a Teflon coating on said surfaces of said fixed vacuum leaf and said plurality of movable leaves. 
     
     
       8. The winding shaft of claim 7, wherein said Teflon coating is a Teflon impregnated Sanford hard lube finish that is about 0.0002 inch thick. 
     
     
       9. The winding shaft of claim 7, wherein said buttons move said radially movable leaf members through a distance of at least about 1/2 inch.